Out-of-hospital cardiac arrest. Use of electrophysiologic testing in the prediction of long-term outcome

The role of silent ischemia, the arrhythmic substrate and the short-long sequence in the genesis of sudden cardiac death

To study the role of silent ischemia and the arrhythmic substrate in the genesis of sudden cardiac death, 67 patients were studied (mean age 62 +/- 12 years). Of these, 14 patients (Group 1) had an in-hospital episode of ventricular tachycardia or fibrillation while wearing a 24 h Holter ambulatory electrocardiographic (ECG) monitor, 33 (Group II) had a documented episode of sustained ventricular tachycardia or fibrillation, or both, and 20 (Group III) had angina pectoris but no ventricular tachycardia or fibrillation. Eight Group I survivors underwent programmed electrical stimulation or ECG signal averaging, or both. All Group II patients underwent 24 h Holter monitoring and ECG signal averaging to detect late potentials before programmed electrical stimulation. Group III patients underwent both 24 h Holter recording and coronary angiography. The 24 h ECG tapes were analyzed for ST segment changes, prematurity index and characteristics of ventricular premature depolarizations. Any ST depression greater than or equal to 1 mm for greater than 30 s was considered to be a reflection of silent ischemia, and the induction of ventricular tachycardia or fibrillation by programmed electrical stimulation or the presence of late potentials, or both, was considered to be a reflection of the arrhythmia substrate. Silent ischemia preceded ventricular tachycardia in only 2 (14%) of the 14 Group I patients. The prematurity index was less than 1 in only 18% of ventricular tachycardia episodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of cardiac arrhythmias: when, how and where?

Despite major advances in the understanding of mechanisms, better diagnostic methods and a wide array of new modes of therapy, management of cardiac arrhythmias continues to be a challenge. Because of possible deleterious effects of antiarrhythmic therapy, the decision about when and how to treat should be weighed carefully with emphasis on symptoms and the prognostic significance of the arrhythmia. When possible, the high risk patient should be referred to a center where expertise and diagnostic and therapeutic possibilities allow optimal treatment.

Significance of the clinical presentation in ventricular tachycardia/fibrillation

We examined the hypothesis that clinical presentation in patients with sustained ventricular tachycardia/fibrillation (VT/VF) predicts clinical, electrophysiologic (EP) findings and long-term outcome. We included in the study 121 consecutive patients seen in our EP laboratory with documented and inducible sustained VT/VF. Patients were categorized into three groups according to their clinical presentation: (1) cardiac arrest (CA)-53 patients; (2) syncope (S)-20 patients; (3) palpitations/dizziness (P)-48 patients. There were no significant differences in age, sex, or prevalence of underlying heart disease between groups. The left ventricular ejection fraction (LVEF) was significantly lower for patients with CA (mean +/- S.D.; 31 +/- 14%) or S (30 +/- 11%) when compared with P (39 +/- 15%) (p less than 0.05). Induction of VT/VF required a more aggressive stimulation protocol (three extrastimuli) in patients with CA (53%) when compared with patients with S (30%) or P (29%) (p less than 0.05). The cycle length of the induced VT was shorter for CA (239 +/- 64 msec) patients as compared with the S (294 +/- 67 msec) or the P (319 +/- 94 msec) patients (p less than 0.01). Polymorphic VT or VF was induced in 28% of CA patients, in 9% of S patients, and in 12% of P patients (p less than 0.05). There were significantly more sudden deaths observed during the 4-year follow-up interval in patients presenting with CA compared to the P group (p less than 0.05). The 4-year survival was 67 +/- 8% for P, 45 +/- 15% for S, and 45 +/- 10% for CA patients (N.S.).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical experience in seventy-seven patients with the automatic implantable cardioverter defibrillator

Seventy-seven patients with drug-refractory sustained ventricular tachycardia (VT) (28 patients) or ventricular fibrillation (VF) (49 patients) underwent implantation of an automatic cardioverter defibrillator (AICD). The 67 men and 10 women, with a mean age of 60 +/- 12 years (range 18 to 79), had coronary artery disease (60 patients), idiopathic cardiomyopathy (eight patients), mitral valve prolapse (four patients), hypertensive heart disease (one patient), Ebstein's anomaly (one patient), long QT syndrome (one patient), and primary electrical disease (two patients). The mean left ventricular ejection fraction was 35 +/- 16% (range 10% to 75%). Sustained VT/VF was induced in 64 patients (83%) at baseline electrophysiologic testing. A mean of 4.1 +/- 1.3 antiarrhythmic drugs failed to control the arrhythmia. Associated surgery at AICD implantation included coronary artery bypass in 19 patients, coronary bypass with aneurysmectomy in six patients, and aneurysmectomy alone in one patient. Five patients had only prophylactic patches implanted during aneurysmectomy or coronary bypass and the AICD device was subsequently implanted under local anesthesia to prevent arrhythmia recurrence or to control persistently inducible VT. Operative mortality was 2.6% with two deaths from intractable VF. Fifty-two patients (69%) continued receiving antiarrhythmic drugs to suppress spontaneous VT. During a mean follow-up of 15 +/- 13 months (range 1 to 63), six patients died: two suddenly due to probable pulse generator failure (greater than 2 years old), one of acute myocardial infarction, two of heart failure, and one of respiratory failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Time-dependent risk of and predictors for cardiac arrest recurrence in survivors of out-of-hospital cardiac arrest with chronic coronary artery disease

One hundred one consecutive patients with chronic coronary artery disease who had survived out-of-hospital cardiac arrest in the absence of acute myocardial infarction underwent electrophysiologic evaluation and were followed prospectively. Ventricular tachyarrhythmias were inducible in 76 patients (75%) in the control state and were suppressed by antiarrhythmic drugs or surgery in 32 of the 76 patients (42%). During a mean follow-up of 27 months, cardiac arrest recurred in 21 patients: in two of the 25 patients in whom ventricular tachyarrhythmias were not inducible in the control state, three of the 32 in whom inducible ventricular tachyarrhythmias were suppressed after treatment, and 16 of the 44 in whom inducible ventricular tachyarrhythmias could not be suppressed after treatment. Actuarial rate of cardiac arrest recurrence was 11.2% during the first 6 months of follow-up ("high-risk early phase") and then decreased to less than 4% in each subsequent 6-month period. Multivariate Cox proportional hazards analysis identified an ejection fraction less than 35% (p = 0.0013) and persistent inducibility of ventricular tachyarrhythmias (p = 0.0025) as independent predictors of cardiac arrest recurrence for the entire follow-up period. Separate analysis of variables within and after the first 6 months showed that an ejection fraction less than 35% was the strongest predictor for early phase recurrence (p = 0.0078) but had only marginally significant predictive value for late phase recurrence (p = 0.0516). Persistent inducibility of ventricular tachyarrhythmias had no significant predictive value for early phase recurrence (p = 0.1382) but was the strongest predictor for late phase recurrence (p = 0.0061). These data suggest that, in patients with chronic coronary artery disease who survive out-of-hospital cardiac arrest, poor ejection fraction and persistent inducibility of ventricular tachyarrhythmias have a different predictive influence on early and late phase recurrence. Time-dependent risk factor analysis may have great clinical relevance in assessing an individual's changing risk over time.

Effect of selective intracoronary antiarrhythmic drug administration in sustained ventricular tachycardia

The effect of selective intracoronary antiarrhythmic drug infusion on inducibility of cardiac arrhythmias was studied in 3 patients with recurrent sustained monomorphic ventricular tachycardia referred for comprehensive electrophysiologic studies. Each patient had evidence of prior myocardial infarction, 1 or more occluded coronary arteries and a readily identifiable collateral vessel that provided collateral flow to the infarct-related artery. In each patient, the clinical arrhythmia was reproducibly inducible by programmed stimulation in the control state. After positioning a small infusion catheter in the collateral vessel, selective intracoronary lidocaine 0.3 to 0.6 mg/min (patients 1 and 2) or procainamide 0.1 to 1.4 mg/min (patient 3) was infused for a 10-minute period. In each patient the clinical arrhythmia was rendered noninducible during selective intracoronary drug infusion. The arrhythmia was again inducible after a 10-minute drug-washout period and also after standard intravenous doses of antiarrhythmic drug. Selective intracoronary antiarrhythmic drug infusion may help to localize the site of origin of some cardiac arrhythmias, may provide a means of testing the effects of several drugs during a single study and may be a new method for studying mechanisms of action of antiarrhythmic drugs.

Antiarrhythmic efficacy of solitary beta-adrenergic blockade for patients with sustained ventricular tachyarrhythmias

To assess the efficacy and predictability of solitary beta-adrenergic blocker (BB) therapy for ventricular tachyarrhythmia (VT), 30 patients (16 men and 14 women) with a mean age of 55 years, who initially had sustained ventricular tachycardia (70%) or ventricular fibrillation (30%), were studied. Results of baseline arrhythmia tests showed VT on ECG monitoring in 57% of the patients, during exercise in 50%, induced by programmed stimulation in 69%, increasing to 86% during isoproterenol. BB therapy prevented inducible VT during programmed stimulation in 37% of the patients, prevented VT on ECG monitoring in 54%, and prevented VT during exercise in 83%. Long-term BB therapy was given to 24 of 30 patients, whereas six other patients with hemodynamically unstable VT during BB therapy received other long-term treatment. During a mean follow-up of 824 days, 6 of 24 patients had recurrent VT. BB therapy was discontinued in two patients because of side effects. Long-term success was predicted by left ventricular ejection fraction greater than 45%, absence of coronary disease, and age less than 60 years (all p less than 0.02). Neither suppression of arrhythmia during exercise testing, nor results of programmed stimulation or ECG monitoring were predictive of outcome. Thus beta-adrenergic blockers can be effective as solitary antiarrhythmic therapy in selected patients with VT.

Young adult survivors of sudden cardiac arrest: analysis of invasive evaluation of 22 subjects

Twenty-two young adult (mean age 27.8 +/- 5.3 years) survivors of sudden cardiac arrest underwent invasive cardiac assessment. Initial evaluation by cardiac catheterization, coronary angiography, and hemodynamic studies identified two groups of young survivors. The first consisted of 13 (60%) subjects who had definable structural cardiac or lung disease accountable for a cardiac arrest event. Dilated cardiomyopathy dominated this group. Mitral valve prolapse, hypertrophic cardiomyopathy, left ventricular hypertrophy, anomalous origin of the right coronary artery, and tetralogy of Fallot were also encountered. The second group included nine subjects (40%) with normal cardiac structure and normal hemodynamic parameters. Electrophysiologic testing demonstrated in three of these patients the presence of Wolff-Parkinson-White syndrome. The electrophysiologic studies had a higher yield in reproduction of life-threatening arrhythmias among the subjects in the second group as opposed to the first group. The observation that 10 subjects (45%) from both groups had preceding symptoms varying from palpitations and chest pain to syncope and recurrent cardiac arrest events, is in contradiction to previous findings in the literature and raises a question of appropriate evaluation of young adults with cardiac symptoms.

Surgical therapy for drug-refractory ventricular tachycardia: results with mapping-guided subendocardial resection

Surgical therapy with mapping-guided subendocardial resection was used in 30 patients with drug-refractory ventricular tachycardia. Results of preoperative, intraoperative and postoperative electrophysiologic evaluation and long-term clinical follow-up are reported. Left ventricular aneurysm was located in the inferior wall in 8 patients and in the anterior wall in 22. Left ventricular mapping was performed in 15 patients preoperatively and in all 30 patients intraoperatively. Subendocardial resection was supplemented with cryoablation in 26 patients and with laser photocoagulation in 4. Coronary bypass surgery was performed in 27 patients. The surgical mortality rate was 10%; the three deaths were due to cardiogenic shock, pneumonia and sepsis, respectively. At postoperative electrophysiologic study, ventricular tachycardia was inducible in 8 (30%) of 27 patients. Previously ineffective antiarrhythmic drugs were effective in preventing the induction of ventricular tachycardia in four of these eight patients. Two of the remaining four patients received an automatic implantable cardioverterdefibrillator; the other two were treated with amiodarone. At a mean follow-up period of 18 +/- 17 months (range 1 to 52), there has been one sudden death and one nonfatal recurrence of ventricular tachycardia in the 18 patients without inducible arrhythmias postoperatively. Among the eight patients with inducible ventricular tachycardia after subendocardial resection, there has been one nonfatal ventricular tachycardia recurrence. Thus, among the 27 patients surviving surgery, 17 (63%) were cured with surgery alone, and another 7 (26%) had their ventricular tachycardia controlled with drugs (n = 5) or the defibrillator (n = 2). Inability to completely map the tachycardia, a clinical history of cardiac arrest requiring resuscitation and the presence of myocardial infarction within 2 months predicted postoperative arrhythmia inducibility and recurrence.

Nonventricular arrhythmias as precursors of ventricular fibrillation in patients with out-of-hospital cardiac arrest

Ventricular tachycardia (VT) and ventricular fibrillation (VF) are the most common arrhythmias documented at the time of resuscitation in survivors of out-of-hospital cardiac arrest unassociated with an acute myocardial infarction. However, 20% and 40% of these patients will not manifest inducible ventricular arrhythmias during subsequent electrophysiologic studies. The optimal management of these patients has been controversial. In a consecutive series of 100 survivors of out-of-hospital cardiac arrest with documented VF, six were identified by either clinical or electrophysiologic data as having a nonventricular arrhythmia as the immediate precursor of VF. Two of these patients had rapid, hypotensive supraventricular arrhythmias induced with programmed cardiac stimulation. In four patients, bradyarrhythmias (sinus arrest two; atrioventricular block two) preceded and caused the episode of VF. Therapy directed at these nonventricular arrhythmias prevented recurrence of cardiac arrest in all patients. In survivors of out-of-hospital cardiac arrest, nonventricular arrhythmias represent a treatable potential etiology that may be overlooked during the patient's evaluation.

Coronary artery bypass grafting in patients with ventricular fibrillation

The role of coronary artery revascularization in the management of survivors of cardiac arrest remains controversial. Patients with sustained monomorphic ventricular tachycardia rarely respond to revascularization, but the response of patients with ventricular fibrillation as their basic arrhythmia has not been characterized. Coronary artery bypass grafting was performed in 8 patients with a history of cardiac arrest known to be caused by ventricular fibrillation without preceding sustained monomorphic ventricular tachycardia. All patients had critical double-vessel or triple-vessel coronary artery disease, and 7 of 8 had wall motion abnormalities from a prior myocardial infarction. After successful operation, 5 patients had no spontaneous arrhythmias and no inducible arrhythmias at a postoperative electrophysiological study. Three patients, however, had spontaneous, recurrent episodes of ventricular fibrillation unassociated with recurrent ischemia. Clinical factors were not useful predictors of response. The effect of coronary artery revascularization in patients with ventricular fibrillation is unpredictable, and full postoperative electrophysiological evaluation is necessary to judge the success of the procedure.

Comparison of immediate versus day to day variability of ventricular tachycardia induction by programmed stimulation

The use of programmed stimulation to assess long-term oral antiarrhythmic drug efficacy for ventricular tachycardia is complicated by the fact that mode of ventricular tachycardia induction varies from day to day in the absence of drug therapy. The purpose of this prospective study was to assess whether mode of ventricular tachycardia induction is more reproducible within one study than from day to day. Thirty-nine consecutive patients with documented sustained ventricular tachyarrhythmias secondary to coronary artery disease underwent three inductions of ventricular tachycardia at 15 min intervals in the absence of drug therapy. A stimulation protocol in which the only major variable was the number of extrastimuli required for tachycardia induction was used. Subsequent day to day variability in mode of tachycardia induction was also assessed in the same patients at two further drug-free inductions at intervals of 5 +/- 2 days. The number of extrastimuli required for tachycardia induction was significantly more reproducible at the immediate repeat studies than from day to day (69% of patients versus 31%, p less than 0.01). From these data, probability tables were derived that show the likelihood that changes in inducibility at subsequent tachycardia inductions are due to chance. The QRS configuration of induced ventricular tachycardia was also more reproducible at the immediate studies (64% versus 26%, p less than 0.01). Basic electrophysiologic and stimulation variables differed over a significantly wider range from day to day than at the immediate studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of malignant ventricular arrhythmias with the automatic implantable cardioverter defibrillator

Twenty-eight patients with malignant ventricular arrhythmias were treated with the automatic implantable cardioverter-defibrillator (AICD) in a 14-month period. Thirteen patients were resuscitated from a ventricular fibrillation (VF) episode. Fifteen patients presented with ventricular tachycardia (VT) refractory to medical therapy. The etiology was coronary artery disease in 23 of 28 patients (82%), dilated cardiomyopathy in 2 of 28 patients (7%), sarcoidosis in 2 of 28 patients, and 1 patient in 28 had lupus erythmatosis. The mean left ventricular ejection fraction was 29%. A total of 27 of 28 patients (96%) patients had inducible ventricular tachycardia using programmed stimulation. The patients considered for AICD implant failed a mean of 3.6 antiarrhythmic drugs. Rate counting and defibrillating leads were inserted through a lateral thoracotomy in 17 patients and a mediansternotomy incision in 11 patients in conjunction with another cardiac procedure in 10 patients. The generators were positioned in a subcutaneous pocket beneath the left costal margin. There were no operative deaths. The mean follow-up was 6.7 months (range 1 to 14) with no VT/VF deaths in patients with defibrillators. The study demonstrated that AICD is an effective device for prevention of sudden cardiac death.

Long-term outcome with the automatic implantable cardioverter-defibrillator

The automatic implantable cardioverter-defibrillator was implanted in 270 patients because of life-threatening arrhythmias over a 7 year period. There was a history of sustained ventricular tachycardia or fibrillation, or both, in 96% of these patients, 80% had one or more prior cardiac arrests and 78% had coronary artery disease as their underlying diagnosis. The average ejection fraction was 34%, and 96% of these patients had had an average of 3.4 antiarrhythmic drug failures per patient before defibrillator implantation. There were four perioperative deaths and eight patients had generator infection or generator erosion, or both, during the perioperative period or during long-term follow-up. Concomitant antiarrhythmic drug therapy was given to 69% of patients. Shocks from the device were given to 58% of patients. and 20% received "problematic" shocks. The device was removed from 16 patients during long-term follow-up for a variety of reasons. There were 7 sudden cardiac deaths and 30 nonsudden cardiac deaths, 18 of which were secondary to congestive heart failure. The actuarial incidence of sudden death, total cardiac death and total mortality from all causes was 1%, 7% and 8%, respectively, at 1 year, and 4%, 24% and 26% at 5 years. The automatic implantable cardioverter-defibrillator nearly eliminates sudden death over a long-term follow-up period in a high risk group of patients. It has an acceptable rate of complications or problems, or both, and most late deaths in these patients are nonsudden and of cardiovascular origin.

Coronary revascularization and implantation of the automatic cardioverter/defibrillator: reliability of immediate intraoperative testing

Concomitant coronary revascularization and implantation of the automatic cardioverter/defibrillator is an increasingly common procedure. To determine whether cardioversion/defibrillation thresholds measured after weaning patients from cardiopulmonary bypass are sufficient to justify immediate implantation of the pulse generator, we prospectively compared postpump values to those obtained 1 week later in five patients. R-wave amplitudes during both sinus rhythm and ventricular tachycardia, lead impedance, defibrillation thresholds and cardioversion thresholds remained stable or improved from the postpump to the 1 week values. Five other patients had the generator implanted at the time of revascularization. Immediate postbypass cardioversion thresholds (mean 10 +/- 8 joules) in these ten patients did not significantly differ from those of 20 nonpump implantations (VT mean 7 +/- joules; VF 15 +/- 4 joules and defibrillation thresholds mean 17 +/- 6 joules). These findings suggest that the residual effects of cardioplegia, core-cooling and operative ischemia have no significant effects on intraoperative testing of implanted defibrillators. This clinical experience supports the practice of immediate implantation of the pulse generator at the time of revascularization.

Psychophysiological factors in ventricular arrhythmias and sudden cardiac death

Plasma catecholamine levels were measured preceding programmed electrophysiological studies of patients who had survived a ventricular tachyarrhythmia episode. Psychological assessments of desire for control, locus of control and behavior pattern were obtained. Psychophysiological variables were analysed with respect to the severity of arrhythmias induced by the electrophysiological procedure. Analysis of data from 17 subjects showed desire for control was significantly higher in those with induced sustained arrhythmias than in those in which nonsustained arrhythmias were induced. No relationship was found between behavior pattern and arrhythmia severity or plasma catecholamine levels. There was a significant interaction between desire for control and behavior pattern with respect to epinephrine level. The findings indicate that psychological factors such as desire for control may be associated with potentially lethal arrhythmias and implicated in sudden cardiac death.

Community study of the causes of "natural" sudden death

Three hundred and fifty cases of "natural" sudden death within six hours of onset of symptoms in people ranging in age from 18 to 69 years in Wandsworth were studied using a detailed necropsy protocol to determine the cause of death. Sudden death occurred in 28 (8%) Asians and blacks, but because of the small number they were excluded from the study, leaving 322 cases. Ischaemic heart disease accounted for 189 (59%) of the 322 sudden deaths (155 (65%) men; 34 (41%) women) and no proportional increase in instantaneous compared with non-instantaneous sudden death was found. Non-ischaemic cardiac disease was the cause of sudden death in 24 cases (7.5%). Non-cardiac disease included pulmonary emboli, aortic aneurysms, and intracerebral haemorrhage and caused 89 (27.6%) deaths. Alcohol was the cause of nine deaths (2.8%) and in 11 (3.4%) cases (six men and five women) no cause of death was found. This study shows that although ischaemic heart disease is the single largest cause of sudden natural death there are other major causes.

Drug therapy for survivors of sudden cardiac death

The proliferation of standard as well as novel community based systems for resuscitation of victims of out-of-hospital cardiac arrest has provided a large group of sudden cardiac death survivors who present a therapeutic challenge. The nature and severity of the underlying heart disease must be delineated. Particularly, myocardial ischemia and congestive heart failure must be controlled. Prior to considering device therapy of surgical intervention, pharmacologic therapy should be evaluated. Baseline electrophysiological studies determine the applicability of serial pharmacologic testing. In patients with inducible VT/VF, serial electrophysiological testing can identify drug regimens that prevent the arrhythmia in approximately 40% of patients. In an additional 20% of patients, regimens which slow the ventricular tachycardia and significantly reduce the arrhythmia related mortality can be identified. Three to 5-year follow-up has shown such an approach can reduce the sudden death mortality in these patients to less than 3% per year. It has been suggested that certain medication, most notably amiodarone, electrophysiological testing has not been useful in assessing efficacy. Several recent studies, however, have shown that electrophysiological testing is indeed useful even in evaluating the efficacy of amiodarone. In patients in whom ventricular tachycardia/ventricular fibrillation cannot be prevented or significantly slowed, medical therapy is generally ineffective and the sudden death mortality is 20% to 40% per year. In such patients, other therapeutic modalities should be considered.

Electrophysiologic evaluation of antiarrhythmic therapy for ventricular tachyarrhythmias

The use of electrophysiologic studies has contributed significantly to our understanding of the mechanisms of ventricular tachyarrhythmias and enhanced our ability to assess objectively the efficacy of various therapeutic interventions in modifying or preventing their recurrence. The basis on which electrophysiologic testing techniques is founded is the ability reproducibility to initiate ventricular arrhythmias by programmed electrical stimulation in patients with a history of recurrent ventricular tachycardia or fibrillation. Ventricular tachycardia can be initiated by electrophysiologic studies in approximately 90% of patients with clinically documented recurrent, sustained ventricular tachycardia related to coronary artery disease and in 60% of patients with nonsustained ventricular tachycardia. Reports indicate that electrophysiologic testing is highly specific as well (99% for sustained monomorphic ventricular tachycardia). Studies in patients with recurrent ventricular tachycardia demonstrate that prevention by antiarrhythmic drugs of the ability to initiate tachycardias that were previously inducible by comparable stimulation techniques in the absence of therapy is highly predictive of freedom from recurrent episodes of spontaneous ventricular tachycardia and ventricular fibrillation. This end point can be achieved in 35 to 75% of patients. This wide range of success rates results from differences in the patient populations studied, as well as major differences in the programmed stimulation and antiarrhythmic drug protocols used among laboratories. The positive predictive value of this technique (defined as the percentage of patients in whom complete suppression of inducible ventricular tachycardia or ventricular fibrillation is achieved during electrophysiologic testing with antiarrhythmic drugs and in whom no spontaneous arrhythmia occurs at 1- to 2-year follow-up) ranges between 80 and 95%.

Clinical predictors of arrhythmia inducibility in survivors of cardiac arrest: importance of gender and prior myocardial infarction

Clinical characteristics that correlate with arrhythmia inducibility were determined in 150 consecutive survivors of cardiac arrest. All underwent electrophysiologic study with a uniform protocol when they were not receiving antiarrhythmic drugs. A ventricular tachyarrhythmia (sustained monomorphic ventricular tachycardia, ventricular fibrillation or nonsustained ventricular tachycardia) was induced in 113 patients (75%). The strongest correlates of inducing a tachyarrhythmia were male gender (p less than 0.0001) and a history of prior myocardial infarction (p less than 0.0001). Induction of sustained monomorphic tachycardia alone was also strongly related to gender and prior infarction; in particular, none of 26 women without prior infarction had induction of sustained monomorphic ventricular tachycardia. Among patients with induced sustained tachyarrhythmias, those with induced monomorphic ventricular tachycardia were distinguished from those with induced ventricular fibrillation in they were more likely to have coronary artery disease (p = 0.0001), healed myocardial infarction (p = 0.0002), left ventricular aneurysm (p = 0.0007) and ventricular tachycardia documented at the time of cardiac arrest (p = 0.02). Other variables showing significant correlations with arrhythmia inducibility were ejection fraction, documentation of ventricular tachycardia at the time of cardiac arrest and presence of an intraventricular conduction delay. However, stepwise logistic regression identified male gender and healed myocardial infarction as the only independent predictors of arrhythmia inducibility. On the basis of these two variables alone, arrhythmia inducibility or noninducibility could be correctly predicted in 89% of the patients in this series.

Value of electropharmacologic testing in idiopathic dilated cardiomyopathy and sustained ventricular tachyarrhythmias

Electrophysiologic studies in 64 patients with idiopathic dilated cardiomyopathy who had sustained ventricular tachycardia or ventricular fibrillation were performed. A sustained ventricular tachyarrhythmia was induced in 43 patients (67%). Electropharmacologic testing predicted an antiarrhythmic drug effective in 15 of 35 patients in whom sustained monomorphic ventricular tachycardia could be induced reproducibly (43% of tested patients, 23% of all patients). During median follow-up of 1.6 years, there were 32 arrhythmia recurrences and 24 cardiac arrests. Multivariate regression analysis identified treatment with a drug predicted to be effective at electropharmacologic testing as the only predictor of freedom from arrhythmia recurrence (p = 0.01); and treatment with a drug predicted to be effective at electropharmacologic testing and lower New York Heart Association functional class as independent predictors of freedom from cardiac arrest (p = 0.03 and p = 0.02, respectively). At median follow-up, the incidences of freedom from arrhythmia recurrence and from cardiac arrest were both 100% during treatment with a drug predicted to be effective at electropharmacologic testing versus 54 +/- 8% and 62 +/- 7%, respectively, during other treatments. These findings indicate that results of electropharmacologic testing accurately predict freedom from arrhythmia recurrence and cardiac arrest in patients with idiopathic dilated cardiomyopathy and sustained ventricular tachyarrhythmias.

Predictors of automatic implantable cardioverter defibrillator discharge for life-threatening ventricular arrhythmias

Data from 100 patients with life-threatening ventricular arrhythmias and automatic implantable cardioverter defibrillators (AICDs) were analyzed to determine if clinical, angiographic and electrophysiologic variables are predictive of AICD discharge. During a median follow-up period of 18 months, 45% of patients experienced greater than or equal to 1 device discharge during a documented ventricular arrhythmia or in association with presyncope or syncope ("appropriate" AICD discharge). Univariate predictors of appropriate AICD discharge included depressed left ventricular ejection fraction (p = 0.0007), inducible sustained ventricular arrhythmia at electrophysiologic study performed in the absence of antiarrhythmic drugs (p = 0.009), fewer number of extrastimuli required for induction at this study (p = 0.001), inducible sustained arrhythmia at electrophysiologic study performed on the discharge antiarrhythmic regimen (p = 0.0005) and fewer extrastimuli required for this induction (p less than 0.0001). Multivariate analysis identified the induction of a sustained ventricular arrhythmia by 1 or 2 extrastimuli during electrophysiologic study performed on the discharge regimen as the only independent predictor among the variables analyzed (p less than 0.0001). The probability of appropriate AICD discharge at 18 months was 86% for patients who had a sustained arrhythmia induced with 1 or 2 extrastimuli versus 15% for those requiring 3 extrastimuli for arrhythmia induction and 13% for patients without inducible sustained arrhythmias.